Vol. 15—1961 - NorthEastern Weed Science Society

276.
COMPARISONS OF PRE-EMERGENCE HERBICIDES
FORTHECONTROL OF CRABGRASS 1
John F. Ahrens and A.' R. Olson2
Homeownerinterest in chemicals for the control of crabgrasa in turf has
increased greatly over the past few years. Public requests for information on
this subject have correspondingly increased. To fill the need for more information
in this area tests were started in 1960 with several pre-emergence
herbicides.
. Proeedure
A series of plots were set up on established turf at the Station grounds
in NewHaven, at Mt. Carmel, and in South Windsor. Plots were at least 4 feet
wide.J:Uld.12fee:tlong •. Alternate plpts ~emained untreated. The number.of
replications varied fxtom3 to 5, depending on the treatment.
The materials
used were as followsr
a) Zytron, 8%granular formulation on vermiculite
b) Dacthal, 1.5%granularformu;Lation
c) IIHalts," a material composedof 23%chlordane on vermiculite
d) "Bonide chlordane, II containing 72%chlordane as emulsifiable concentrate
e) tlPax,lt a.material containing 25.11% arsenous oxide, 8.25% arsenate of
lead, 0.34% heptachlor, and 8.0% ammoniumsulfate
f) IINoCrab," a material containing 47.22% caloium arsenate, 0.38% 2,4-D,
and 0.13% silvex
The dry formulations were applied with a 2-foot lawn spreader, calibrated
for each material. The liquid formula.~o,p at ct1lordane Wasapplied iJl. 390 .
gallons of solution per aore;with a watering oan.
1'1osttreatmentsvere appl..ied on Apr~l:., 26.~ 29, before any~$grass had
emerged. However, calcium arsenate and one dosage of chlordane were applied
on May17, when orabgrass was emerging in some plots. In one area, half of
each plot.was. ... $..:tered.after. treatment. .
The established turf consisted of a mixture of Kentucky bluegrass, fescue
grasses and benbgz-asa •. To encourage. crabgrass invasion, these ,areas were mowed
to a height of 3/4 to 1 inch in Nay and June, and slightly higher thereafter.
The plots were fertilized in. early spring according to soil tests.
1. Contribution of The Conneoticut Agricultural Experiment Station, NewHaven,
Connecticut.
2. Assistant Plant Physiologist and Assistant Forester, respectively.